1. Field of the Invention
This invention relates to a solid state memory device which does not require a mechanical driving portion.
2. Description of the Prior Art
A magnetic bubble memory element, a magneto optical disc memory device or the like is known as a solid state memory. The magnetic bubble memory element has a great memory capacity, but it has suffered from a disadvantage of low transfer speed because it usually forms major and minor loops and transfers bubbles along a predetermined pattern by an external rotational magnetic field. Accordingly, even in the conventional element of the highest speed, the transfer speed is of the order of 1 mega bit/sec. and such element cannot meet the recent demand. On the other hand, in a magneto-optical disc memory device using a vertical magnetic memory material, such as a magneto-optical disc of a diameter of 20 cm using an amorphous magnetic medium, storage and reproduction at a speed of 10 mega bits/sec. becomes possible at 1800 rpm, and a great capacity and a high transfer speed are obtained. However, such magneto-optical disc memory has a mechanical driving portion and requires a control system for autofocusing, autotracking, etc., and this has led to the complexity and expensiveness of the device.